If said tweets were reported they would (probably?) be deleted. I'm not sure the "custom tool" defense would really work, you could say the same thing for warez on usenet or even simple jpegs and videos, you need special codecs to view them. Furthermore even plain text embedded in the chain might be enough to get you in trouble in some jurisdiction if it contains hate speech, personal info or harassment material for instance.
The problem with the blockchain is actually its greatest strength: it's immutable. If somebody reports a block containing child porn there's no way to remove it without compromising the blockchain's integrity.
What's meant by "containing"? Regular wallet software doesn't allow access to anything besides transaction data. You won't be able to view any text or images.
The number "Pi" contains all hate speech and other illegal content imaginable.
I'm not a lawyer, I'm not sure what will and won't hold up in court. I think the main problem would be if you operate a node that's not just a consumer but also uploads blocks, it could be argued that you distribute the potentially infringing content. At this point your ability to actually view the content yourself is moot. You're basically operating a peer-to-peer network that can be used to distribute arbitrary data.
>The number "Pi" contains all hate speech and other illegal content imaginable.
That's irrelevant. If you don't think so try downloading child porn, get caught and argue that "it's just decimals of Pi!". Report back with results.
Just to clarify because this is widely misunderstood - hate speech is not a crime in America. Though it is in other western countries like Germany and New Zealand.
The problem with the blockchain is actually its greatest strength: it's immutable. If somebody reports a block containing child porn there's no way to remove it without compromising the blockchain's integrity.